The trio looked at a hypothetical network of 200 banks, each represented by a simple mathematical model. The model divided a bank's financial position into assets, liabilities and capital. Assets included holdings in the form of cash or investments, as well as money lent to other banks. Liabilities covered anything that really belonged to someone else, such as deposits made by customers or money borrowed from other banks. Finally, capital measured the investment made by the bank's shareholders. The bank's finances followed the basic accounting equation, which underpins all modern bookkeeping: Assets = Liabilities + Capital.